The present, invention relates generally to the field of semiconductor packaging. More specifically, the present invention relates to an integrated circuit package and a process for forming the same.
Most integrated circuit packages share a substantially standard construction. Specifically, the actual circuitry is on a semiconductor die, which is mounted, usually by adhesive, to a relatively large (as compared to the die) mass or xe2x80x9cslugxe2x80x9d which acts as a heat sink.
The die has a plurality of bond pads through which power, ground, and signals are communicated outside the die. Bond wires are bonded, typically by a process known as xe2x80x9cwirebonding,xe2x80x9d to the bond pads. The other ends of the bond wires are wirebonded to one of a plurality of metallic lead fingers, or package leads, that lay on the heat sinking mass but are separated from it by a non-conductive layer. The nonconductive layer is typically an insulating adhesive tape, although it may be other materials such as a ceramic layer bonded to the heat sinking mass.
The package leads are generally formed by stamping from a single sheet of suitable conductive metal. The portions which are to protrude from the package as pins are joined together by a rectangular band of metal at their outer extremities, forming a unit known as a leadframe. To assemble the integrated circuit package, the insulating layer is applied to the heat sinking mass, and the leadframe is attached in place. The die is subsequently affixed, and the wire leads are wirebonded to the appropriate bond pads and package leads.
The entire assembly is then encased in a plastic or epoxy xe2x80x9cmold compoundxe2x80x9d with ends of the package leads protruding as pins for connection to external devices.
As integrated circuit devices become more complex, the die sizes are becoming smaller. Decreasing die sizes have resulted in finer bond pad pitches, longer bond wire lengths, and closer wire-to-wire separation. At the same time, bond wire diameters are becoming thinner.
With the increase of bond wire span, reduction of bond wire diameter, and reduction in wire-to-wire separation, various problems arise in packaging these integrated circuits. One particularly glaring problem is that, when the bond wires are subject to injection molding, adjacent bond wires may come into contact with each other to form short-circuits.
Accordingly, it would be highly desirable to provide an improved integrated circuit package that overcomes the problems associated with increasing bond wire span, reduced bond wire diameter, and reduced wire-to-wire separation.
The invention provides an improved integrated package and a process for forming the same. According to an embodiment of the invention, a substrate is first provided. A non-conductive lead finger mounting ring is attached to the peripheral region of the substrate. A die attachment pad (DAP) is attached onto the substrate and a plurality of lead fingers are attached to the non-conductive lead finger mounting ring. A semiconductor die is then attached onto the DAP. Bond wires are attached to the semiconductor die and to the lead fingers. An epoxy material is then dispensed over the semiconductor die, forming a protective encapsulation for the bond wires. The epoxy material is then cured. Thereafter, a mold compound is dispensed and molded to form a plastic encapsulation of the package. The epoxy encapsulation protects the bond wires from the mold compound, and prevents adjacent bond wires from short circuiting during the molding process. Thus, the present invention is particularly applicable to semiconductor dies that have a fine pad pitch.
A completed semiconductor package includes a semiconductor die with bond pads, a die attachment pad on which the semiconductor die is attached, and a substrate on which the die attachment pad is positioned. A non-conductive lead finger mounting ring is attached to the peripheral region of the substrate. Lead fingers are coupled to the lead finger mounting ring, and are coupled to the bond pads via bond wires. The bond wires are enclosed in an epoxy material. The die, the die attachment pad, the substrate, the lead finger mounting ring, and the epoxy material are enclosed in a mold compound.